In Asymmetric Digital Subscriber Line (ADSL) and Very-high-bit-rate Digital Subscriber Loop 2(VDSL2) technologies, the initial bearer channel is inherited from Asynchronous Transfer Mode (ATM) technology.
FIG. 1 is a schematic diagram of the ATM mode access of ADSL/IVDSL2in the conventional art. As shown in FIG. 1, when a subscriber access to a network, an ATM mode adaptation is performed in an ADSL/VDSL2 Customer Premise Equipment (CPE) for the datagram of the subscriber, and the subscriber data is borne on the ATM link layer. A common central office access device usually accesses a subscriber device such as a Personal Computer (PC) in the ATM mode, and the CPE also employs the ATM mode.
When more and more subscribers require services occupying higher bandwidth, VDSL2 technology gradually becomes one of the selections of the operation. FIG. 2 is a schematic diagram of the PTM mode access of VDSL2 in the conventional art. As shown in FIG. 2, a Packet Transfer Mode (PTM) based on packet bearer is newly added in VDSL2. The PTM mode is a mode for the future Ethernet access, and the link layer is encapsulated in the Ethernet format.
Considering that the ADSL ATM mode has been widely employed in the existing network, when VDSL2 line services are deployed practically, these services need to be compatible with the original ADSL subscribers. Thus, requirements from two aspects are laid on the deployment of the VDSL2: the first requirement is that the physical layer of the VDSL2 line of the access device AN should be able to automatically identify whether the accessed CPE is in the ATM mode or in the PTM mode, and thus the corresponding configuration can only be made when the operation mode of the terminal is identified; the second requirement is that the service layer should be instructed to implement the automatic service configuration directed to the port when the physical layer of the VDSL2 line of the access device AN identifies the operation mode, because in the ATM mode, the ATM cell is received by the port, and the service configuration and processing are mainly based on the ATM cell, whereas in the PTM mode, an Ethernet packet in the PTM mode is received by the port, and the service configuration and processing are mainly based on the Ethernet packet. Therefore, the service layer should perform automatic adaptation according to the mode identified by the physical link. However, the above two requirements cannot be met in the conventional art.